This invention relates generally to combined cycle power systems and more specifically, to methods and apparatus for cooling a feed injector.
At least some known combined cycle power systems used for power generation include a gasification system that is integrated with at least one power-producing turbine system. For example, known gasifiers convert a mixture of fuel, air or oxygen, steam, and/or limestone into an output of partially combusted gas, sometimes referred to as “syngas.” Hot combustion gases are supplied to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides additional electrical power to the power grid.
At least some known gasification systems use at least one feed injector to supply fuel into a reactor vessel coupled within the gasification system. Known feed injectors are exposed to temperature extremes within the reactor vessel. Specifically, the tips of known feed injectors are exposed to combustion temperatures that may inhibit effective operation of the feed injectors and/or shorten the life span of the feed injectors. Additionally, known feed injectors are also exposed to corrosive elements in the syngas flowing within the reactor vessel. Over time, exposure to such elements may adversely affect the operation and/or shorten the life span of known feed injectors.
To facilitate preventing damage to the feed injectors, at least some known gasification systems use a closed-loop water system to supply cooling water to the feed injector and separate the coolant from the reactor vessel of the gasification system. Generally, such a system includes a heat exchanging apparatus in close proximity to the feed injector. The heat exchange apparatus facilitates recycling water through or near the feed injector such that the water is not allowed to mix with the operational products. However, use of such a system may create a large thermal gradient between the coolant side and the ambient temperature of the injector nozzle, which may induce thermal stresses. Over time, such thermal stresses prematurely shorten the life span of the feed injectors. Other known feed injectors use various alloys to passively prevent the corrosive effects of syngas and its corrosive elements. However, such feed injectors may still be prone to corrosion as a result of carburization, sulfidation, and/or dew point acid attacks.